<?php
$s="123abc汉";
echo $s,"\n";
echo $s[0],$s[3],"\n";
echo $s[-1],$s[-3],"\n";


$s='string';
$s[0]='s';
echo "$s's first character is {$s[0]}\n";
$s[-3]='0000';
echo "$s\n";
$s[8]='!';
echo "$s\n";



echo 'I\'m a student\n',"\n";
echo "He say:\"I'm a teacher\"\n";
$a=123;
$b=6789;
echo "$a+$b=",$a+$b,"\n";
$go="去";
$goo="咕咕的叫声";
$good="好的";
$goods="商品";
echo "{good}s是什么意思？{$goo}ds\n";
$a=['2401','name'=>'张三','age'=>18];
echo "学号:$a[0],姓名:$a[name]，年龄:$a[age]\n";
echo "学号:{$a[0]},姓名:{$a['name']}，年龄:{$a['age']}\n";
$a=[['2401','name'=>'zs'],['age'=>18]];
echo "学号:{$a[0][0]},姓名:{$a[0]['name']}，年龄:{$a[1]['age']}\n";